Decay mechanism and lifetime of ${}^{67}$Kr

Abstract

The lifetime of the recently discovered $2p$ emitter ${}^{67}$Kr was recently found considerably below the lower limit predicted theoretically. This communication addresses this issue.Different separation energy systematics are analyzed and different mechanisms for $2p$ emission are evaluated. It is found that the most plausible reason for this disagreement is a decay mechanism of ${}^{67}$Kr, which is not "true $2p$" emission, but "transition dynamics" on the borderline between true $2p$ and sequential $2p$ decay mechanisms. If this is true, this imposes stringent limits $E_r=1.35-1.42$ MeV on the ground state energy of ${}^{66}$Br relative to the ${}^{65}$Se-$p$ threshold.

Comments: 7 pages, 8 figures